1. WHAT IS MOTION? HOW DO WE DESCRIBE MOTION? Unit 2 - Kinematics SP1. Students will analyze the relationships between force, mass, gravity, and the motion of objects. Calculate avg velocity, instantaneous velocity, and acceleration in a given frame of reference Compare and Contrast scalar and vector quantities. Compare graphically and algebraically the relationships among position, velocity, acceleration, and time.

2. What is Motion? Motion = a change in position In order to describe a change need a Frame of Reference EX: Describe the motion of the pencil.  vs the Sun  vs the Earth ** Most common frame of reference is the surface of the earth

3. Frame of Reference Reference point used to compare distances, displacements, speeds, velocities, etc. To measure motion, one point must be considered as nonmoving

4. Sports use reference points Football? Basketball? Baseball? And many others

5. SCALAR AND VECTOR QUANTITIES describe magnitude only  speed  Time  distance  mass  volume describe magnitude and direction  velocity  acceleration  displacement  forces

6. What is Motion? Distance – total change in position (how far) Displacement – total distance from starting point and direction

7. Distance? 8 m 6 m 2 m 1 m

8. Displacement? 8 m 6 m 2 m 1 m

9. Distance vs. Displacement Examples 6 m3 m Distance= Displacement =9 m9 m right 6 m 3 m Distance= Displacement =9 m3 m left 6 m 3 m Distance= Displacement =9 m?

10. Distance versus Displacement To determine displacement draw a diagram of the path taken  Example: 8 m east, then 6m north, then 2 m east, then 1 m south Simplify the diagram to a right triangle Use Pythagorean Theorem to determine the displacement 8 m 6 m 2 m 1 m

11. Speed and Velocity speed is the rate at which distance is covered scalar quantity velocity is the speed and direction of an object vector quantity

12. Descriptors of Speed/Velocity Instantaneous Velocity  velocity at a given point in time What tools do we use to find the instantaneous speed of a car? Constant Speed  speed that does not change Constant Velocity  speed and direction do not change – perfect straight line motion What three controls in our car change velocity?

13. Acceleration – change in motion any change in velocity is called acceleration  change in speed  change in direction vector quantity has two units of time in the unit!!!!!!!!!

14. Acceleration EQ A car is traveling around a track with it’s cruise control set at 30 m/s. Does the car undergo acceleration? Sample problem: In 5 seconds a car moving in a straight line to the north increase its speed from 50 km/hr to 75 km/hr. What is the magnitude of its acceleration?

15. Free Fall Falling bodies accelerate due to gravity If a body falls under the influence of gravity only, it is said to be in Free Fall We ignore air resistance when studying free fall All bodies in free fall, regardless of weight, will accelerate at the same rate The acceleration due to gravity is: g = 9.8 m/s 2

16. Acceleration-Free Fall Equations When initial velocity is zero, v f = at TIME (s)VELOCITY (m/s) 00 19.8 219.6 329.4 439.6